It is known that, for environmental reasons and comfort of users of gasoline pumps, there is an ever greater tendency to fit, or endeavor to fit hydrocarbon dispensers with systems for recovering and recycling the hydrocarbon vapors released into the atmosphere while filling vehicle tanks.
For effective systems it is necessary to provide pump means in the vapor recovery circuit to assist the transfer of the gaseous substances through the flexible hoses and the dispensing nozzle, which have non-negligible headlosses.
Vapor recovery pumps are subjected to particularly severe operating conditions, which explains the difficulties encountered in their development and the frequent breakdowns occurring with those vapor recovery system that do exist.
Thus the fluid conveyed by aspiration of vapors comprises a mixture of more or less dry air, gaseous hydrocarbons which may condense, as well as dust particles and possibly saline mist. As a result, because of the absence of hydrocarbons in liquid form, the moving parts of the pump are not lubricated, and the gaseous mixture may additionally be corrosive.
Furthermore, to obtain a pumping rate and good volumetric output from the pump at all speeds, it is necessary to have close contact between the various moving parts of the pump, i.e. good sealing between these parts. Moreover, attempts to achieve this sealing and the adjustments effected may lead to non-negligible heating of some of the parts, creating further problems.
To solve these problems it would be necessary for the pump to be lubricated continuously. It will be understood that it is not possible to lubricate such a pump with a more or less viscous oil. In fact such lubricating oil would finish up at the end of the vapor recovery channel in the tank containing the hydrocarbons which are subsequently pumped out to dispense hydrocarbon to the user.
It is an object of the invention to provide a system for recovering vapor in which the pump is effectively and continuously lubricated under acceptable conditions as regarding the lubricating fluid and which moreover does not involve additional energy consumption.